1. Field of the Invention
The present invention generally relates to auto-calibration for analyte measurement by a meter, and, more particularly, to an auto-calibration circuit, such as an auto-calibration label, that provides extended read and decode functionality for a meter.
2. Description of Related Art
The field of clinical chemistry is concerned with the detection and quantization of various substances in body material, typically body fluids such as blood, urine or saliva. In one important aspect of this field, the concentration of naturally occurring substances, such as cholesterol or glucose, in an individual's blood is determined. One of the most frequently used analytical devices in clinical chemistry for determining the concentration of an analyte in a fluid sample is the test sensor. When the test sensor receives the fluid sample, certain reagents incorporated into the sensor react with the analyte in the fluid sample and provides a detectable signal, which indicates the concentration of the analyte. The signal may be a change in color as in the case of a colorimetric sensor or a change in current or potential as in the case of an electrochemical system. Those systems which employ an enzyme in the reagent system may be referred to as biosensors since they rely on the interaction of the enzyme (a biological material) with the analyte to provide the detectable response. This response, whether it be a change in color or in current or in potential, is typically measured by a meter, into which the sensor is inserted. The meter then displays a readout of the corresponding analyte concentration on a graphical user interface.
In particular, the determination of glucose in blood is of great importance to diabetic individuals who must frequently check the level of glucose to regulate their diets and their medications. While the remainder of the disclosure herein may be directed towards the determination of glucose in blood, it is to be understood that the procedure and apparatus of this invention can be used for the determination of other analytes in other body fluids or even non-fluid body materials such as the detection of occult blood in fecal material upon selection of the appropriate enzyme. In addition such sensors can be used in, for example, testing for meat spoilage or foreign substances in well water.
Diagnostic systems, such as blood glucose meters, typically calculate the actual analyte concentration according to a measured output and the known reactivity of the reagent on the test sensor. The reactivity of the reagent, however, may depend on manufacturing variations between lots of test sensors. To account for these variations and ensure proper calculation of the analyte concentration, the diagnostic systems may require some calibration. Various techniques have been used to communicate calibration information to diagnostic systems. The calibration information, for example, may include a code of characters and/or numbers that the diagnostic system translates, via a stored lookup table, into calibration coefficients that are used with equations to calculate the analyte concentration. In some systems, the user of the system may receive and manually enter calibration information into the system. In other systems, a calibration element, which may be similar to a test sensor, may provide readable calibration information when inserted into the system. In yet other systems, a memory element may be connected directly to a processor of the system to provide readable calibration information.